rcu: INFO: rcu_preempt self-detected stall on CPU rcu: 0-...!: (10499 ticks this GP) idle=c1e/1/0x4000000000000002 softirq=12468/12468 fqs=7 (t=10500 jiffies g=7117 q=194) rcu: rcu_preempt kthread starved for 10485 jiffies! g7117 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1 rcu: RCU grace-period kthread stack dump: rcu_preempt R running task 28984 10 2 0x80004000 Call Trace: context_switch kernel/sched/core.c:3385 [inline] __schedule+0x9a0/0xcc0 kernel/sched/core.c:4081 schedule+0x181/0x210 kernel/sched/core.c:4155 schedule_timeout+0x14f/0x240 kernel/time/timer.c:1895 rcu_gp_fqs_loop kernel/rcu/tree.c:1661 [inline] rcu_gp_kthread+0xed8/0x1770 kernel/rcu/tree.c:1821 kthread+0x332/0x350 kernel/kthread.c:255 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352 NMI backtrace for cpu 0 CPU: 0 PID: 8605 Comm: syz-executor.0 Not tainted 5.5.0-rc5-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x1fb/0x318 lib/dump_stack.c:118 nmi_cpu_backtrace+0xaf/0x1a0 lib/nmi_backtrace.c:101 nmi_trigger_cpumask_backtrace+0x174/0x290 lib/nmi_backtrace.c:62 arch_trigger_cpumask_backtrace+0x10/0x20 arch/x86/kernel/apic/hw_nmi.c:38 trigger_single_cpu_backtrace include/linux/nmi.h:164 [inline] rcu_dump_cpu_stacks+0x15a/0x220 kernel/rcu/tree_stall.h:254 print_cpu_stall kernel/rcu/tree_stall.h:455 [inline] check_cpu_stall kernel/rcu/tree_stall.h:529 [inline] rcu_pending kernel/rcu/tree.c:2827 [inline] rcu_sched_clock_irq+0xe25/0x1ad0 kernel/rcu/tree.c:2271 update_process_times+0x12d/0x180 kernel/time/timer.c:1726 tick_sched_handle kernel/time/tick-sched.c:167 [inline] tick_sched_timer+0x263/0x420 kernel/time/tick-sched.c:1310 __run_hrtimer kernel/time/hrtimer.c:1517 [inline] __hrtimer_run_queues+0x403/0x840 kernel/time/hrtimer.c:1579 hrtimer_interrupt+0x38c/0xda0 kernel/time/hrtimer.c:1641 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1110 [inline] smp_apic_timer_interrupt+0x109/0x280 arch/x86/kernel/apic/apic.c:1135 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:829 RIP: 0010:__memcg_kmem_uncharge+0x8/0x1a0 mm/memcontrol.c:2908 Code: 07 00 74 12 48 81 c3 08 02 00 00 48 89 df 4c 89 f6 e8 8c 85 ff ff 5b 41 5e 5d c3 0f 1f 80 00 00 00 00 55 48 89 e5 41 57 41 56 <41> 55 41 54 53 50 89 f3 49 89 fc 48 b8 00 00 00 00 00 fc ff df 4c RSP: 0018:ffffc90002137430 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13 RAX: ffffffff81489244 RBX: ffffea0002673280 RCX: 0000000000040000 RDX: ffffc90001f19000 RSI: 0000000000000000 RDI: ffffea0002673280 RBP: ffffc90002137440 R08: 000000000003a728 R09: ffffed10112c56b1 R10: ffffed10112c56b1 R11: 0000000000000000 R12: ffff8880a2568020 R13: dffffc0000000000 R14: 1ffff110144ad004 R15: ffff88808962b578 memcg_kmem_uncharge include/linux/memcontrol.h:1402 [inline] free_thread_stack+0x12e/0x590 kernel/fork.c:284 release_task_stack kernel/fork.c:440 [inline] put_task_stack+0xa3/0x130 kernel/fork.c:451 finish_task_switch+0x3f1/0x550 kernel/sched/core.c:3256 context_switch kernel/sched/core.c:3388 [inline] __schedule+0x9a8/0xcc0 kernel/sched/core.c:4081 preempt_schedule_common kernel/sched/core.c:4236 [inline] preempt_schedule+0xdb/0x120 kernel/sched/core.c:4261 ___preempt_schedule+0x16/0x18 arch/x86/entry/thunk_64.S:50 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:161 [inline] _raw_spin_unlock_irqrestore+0xcc/0xe0 kernel/locking/spinlock.c:191 spin_unlock_irqrestore include/linux/spinlock.h:393 [inline] pwq_adjust_max_active+0x791/0x8d0 kernel/workqueue.c:3726 link_pwq kernel/workqueue.c:3762 [inline] numa_pwq_tbl_install+0x217/0x430 kernel/workqueue.c:3854 apply_wqattrs_commit+0x1d2/0x570 kernel/workqueue.c:3969 apply_workqueue_attrs_locked+0xdc/0x650 kernel/workqueue.c:4014 apply_workqueue_attrs kernel/workqueue.c:4046 [inline] alloc_and_link_pwqs kernel/workqueue.c:4164 [inline] alloc_workqueue+0xddc/0x1310 kernel/workqueue.c:4278 ucma_open+0x8c/0x1f0 drivers/infiniband/core/ucma.c:1720 misc_open+0x3ef/0x440 drivers/char/misc.c:141 chrdev_open+0x509/0x590 fs/char_dev.c:414 do_dentry_open+0x740/0x10c0 fs/open.c:797 vfs_open+0x73/0x80 fs/open.c:914 do_last fs/namei.c:3420 [inline] path_openat+0x1387/0x4240 fs/namei.c:3537 do_filp_open+0x192/0x3d0 fs/namei.c:3567 do_sys_open+0x29f/0x560 fs/open.c:1097 __do_sys_openat fs/open.c:1124 [inline] __se_sys_openat fs/open.c:1118 [inline] __x64_sys_openat+0xa2/0xb0 fs/open.c:1118 do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x45af49 Code: ad b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007f7b37fdec78 EFLAGS: 00000246 ORIG_RAX: 0000000000000101 RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 000000000045af49 RDX: 0000000000000002 RSI: 0000000020000180 RDI: ffffffffffffff9c RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007f7b37fdf6d4 R13: 00000000004c8ab8 R14: 00000000004e10f8 R15: 00000000ffffffff